Method and apparatus for buffering media

Abstract: An apparatus buffers the movement of sheets cut from a continuous web. Each sheet has a sheet leading edge and a sheet trailing edge. Feeding means (26) are provided for feeding the web leading edge into a buffer (40) at a first speed. Cutting means (16) cut said web to form a first sheet having said sheet leading edge and said sheet trailing edge, and to form a new web leading edge. A single pair of roller means (46) grab and hold said web leading edge when it first enters said buffer (40) at said first speed and for then advancing said sheet leading edge of said first sheet out of said buffer at a second speed. Said feeding means (26) feed said new web leading edge into said buffer at said first speed while said sheet trailing edge of said first sheet is advancing out of said buffer at said second speed.

Description: This invention relates to the movement of sheets of material from a first machine operating at a first speed to a second machine operating at a second speed and provides a method and apparatus to allow each machine to operate at its own speed with no idle time of either machine. An example is automated photographic imaging and developing. The forming of a photographic latent image in a first machine by exposing photographic material to exposure illumination and the subsequent chemical developing of the latent image in a second machine that develops, fixes, and washes the latent image forming a silver image, are consecutive processes, which usually occur at different operating speeds. The diffusion transfer reversal (DTR) process as described in U.S.-A-2,352,014 is a photo-chemical process of exposing a photosensitive material to electromagnetic radiation thereby forming a latent image and then chemically processing the latent image in a subsequent step, thereby forming a silver image. Similar photochemical processing methods are used for example in photo finishing applications and in electronic prepress systems. In such applications film images are produced for transfer to lithographic plate materials or for imaging photolithograph plates directly. In electronic prepress systems, images to be printed by offset printing means are scanned from photographic negatives and digitized, assembled and edited electronically at a work-station, and then transmitted to a raster image processor or "RIP" for half-tone screening and image rasterization. The "RIP image", that is, the rasterized image to be printed, is then transmitted from the RIP to an imagesetter for photographic or film recording. Such an electronic prepress system is described in U.S. Patent No. 4,004,079 and is available for example from MILES Inc. under the Trademark "COLORSCAPE". An imagesetter includes a supply of unexposed photosensitive material, a recording support surface, and an image exposing system for forming the image to be recorded according to the RIP image data. The image exposing system may employ a laser beam, a cathode ray tube (CRT), an LED emitter or the like as a radiation source. The material passes from a supply roll or web to the recording support surface at which point the photosensitive material is exposed to the recording radiation, forming a latent image. The speed of the web movement is determined by the image resolution which may vary from image to image. Numerous images may be recorded onto the web consecutively, each image having a variable length of unexposed web there between which is controlled by the imagesetter controller. The exposed material advances onto a take-up cassette that takes up the entire length of recording material and maintains it in light-tight environment. The take-up cassette is then removed and transported from the imagesetter to the film processor where the chemical processing occurs at a constant speed. The processor passes the material at a constant speed so that the chemical processing necessary for developing and fixing occurs at predetermined rates. According to this system, the web is wound onto the take-up cassette at the speed of the imagesetter which may vary from image to image, and after transportation, is removed from the take-up cassette at the constant speed of the processor. Additionally, after the developing occurs in the processor, the entire length of recording material must be cut into sheets to separate the images. This requires two manual steps that slow operation. Consequently, a single phase buffer was developed that provides a bridge from the imagesetter directly to the processor, similar to UK Patent Application GB-A-2,100,882. Here, the RIP image is recorded onto the web material, advanced to a cutter within the imagesetter, cut, and fed into the bridge. The light-tight single phase buffer receives a latent image on a cut sheet of the web material at the imagesetter speed, and then the processor takes the sheet from the bridge at the processor operating speed. This overcomes the problem of transporting the take up cassette and cutting the images manually. However, the single phase buffer is limited to transferring only one sheet at a time. Additionally, the imagesetter remains idle while the entire first sheet is processed since the bridge must be completely cleared due to the imagesetter typically running faster than the processor. Although this method provides automation, it still slows the overall operation. Another disadvantage of the single phase buffer is that the length of the film that can be taken into the buffer is limited to the approximate length of the bridge. Therefore, after the imaging is complete, the film is advanced to the cutter, cut, and then delivered to the buffer. The end of the image is advanced from the imaging point to the cutting point within the imagesetter, during which time no imaging occurs. The film is then cut, leaving a large unexposed area of film at the leading edge of the web from behind the cutter back to the imaging point; a result of the advancement of the film to be cut from the web. Because this cycle of advancing and cutting occurs often, there are frequent unexposed areas of film. From JP-A-62-70155, which corresponds to US-A-4,723,153 and DE-A-36 32 198, which forms the closest prior art and has been used for the formulation of the preamble of the independent claims, it is known to convey a photographic paper sheet with no stagnation by feeding a continuous photographic paper sheet into a developing section after printing, through a first loop section, a first conveying roller, a second loop section and a second conveying roller in the mentioned order. A flap 70 serves for feeding a printed photographic paper sheet in between first two clamping rollers, and, in a different position thereof, for feeding said paper in between second clamping rollers. In a third position thereof, said flap 70 takes a vertical position. DE-A-37 19 998 describes an apparatus for transporting photosensitive material in which end sections of said exposed material are pressed against a drum surface by means of pressing rods. For causing the material to form a loop, a loop-forming plate is provided which - under the increasing weight of the photosensitive material resting thereon - gradually tilts downward, thus allowing the material to slide down therefrom. DE-A-37 18 644 discloses a method for transporting a strip of photosensitive copying paper within a copier in which the front end of a paper strip is clamped onto a rotary element by means of pressing contact arms. After rotation about a predetermined angle, said rotary element is then halted so as to allow an individual loop to be formed. It is accordingly an object of this invention to minimize unexposed areas of film by buffering longer lengths of film than the single phase buffer, each length having several consecutive images, thereby reducing the frequency of advancing and cutting the film. The solution for the above problem is given by an apparatus having the features of claim 1 and a method having the features of claim 9. Alternatively, a cut may be made between every image. Here a small gap of unexposed web, or an interimage space, is left in between images as a designated cutting location. As the gap moves from the imaging point to the cutting point, the imagesetter is forming. When the gap arrives at the cutter, the imaging is suspended temporarily to cut at the approximate center of the gap. By this method, large unexposed areas are eliminated, and the delay in imaging is virtually instantaneous. It is an advantage of this invention to provide communication between the buffer, imagesetter and film processor. Communication between the buffer, imagesetter and processor allows for two sheets of film to be buffered consecutively and automatically without the imagesetter standing idle while waiting for the buffer to clear completely. It is a specific advantage of the invention to maximize the operating time of the imagesetter. The imaging activity is interrupted for short periods of time due to the buffer. The buffer transports the media from a first storage space to a second storage space at a speed much faster than the speed at which the imaging occurs, thus imaging may continue shortly thereafter. It is another specific advantage of the invention to provide an internal buffer integral with an imagesetter. The buffer is designed to fit in the space of and replace the take-up cassette of the imagesetter thereby allowing an operator to operate the imagesetter with or without a processor, if so desired. This reduces the number of components in the photographic imaging and developing system with speed differential compensation and reduces the required floor space of the overall system which is a critical consideration in many prepress installations. It is a specific advantage of the invention to prevent a pair of drive rollers from jerking the film and disrupting the ongoing imaging. The film coming out of the imagesetter may be required to oscillate back and forth in a positive and negative direction relative to its direction of travel because of the imaging requirements or the media transport system. This makes it necessary to provide a preliminary slack in the film before the drive rollers grab the film. Then, if the film is moving in a negative direction at the instant when the drive rollers grab the leading edge the preliminary slack is sufficient to prevent the drive rollers 10 from jerking the film and disrupting the ongoing imaging. It is another specific advantage of the invention to account for the natural curvature of the film. Complicating the step of the drive rollers taking up the film is the inherent natural curvature of the film which is especially pronounced at the leading edge of the web supply roll. To guide the film into the drive rollers, the film is preformed by a curved guide into a shape which will grow into a downward slack loop, when the drive rollers hold the leading edge in place and the film is continuously entering from the imagesetter. The invention involves an apparatus and method for buffering the movement of sheets cut from a continuous web, the continuous web having a web leading edge, and each sheet having a sheet leading edge and a sheet trailing edge, comprising a feeding mechanism for feeding the web leading edge into a buffer at a first speed, a cutting mechanism for cutting the web to form a first sheet having a sheet leading edge and a sheet trailing edge, and to form a new web leading edge, and a single pair of rollers for grabbing and holding the web leading edge when it first enters the buffer at the first speed and for then advancing the sheet leading edge of the first sheet out of the buffer at a second speed, the feeding mechanism feeding the new web leading edge into the buffer at the first speed while the sheet trailing edge of the first sheet is advancing out of the buffer at the second speed. More particulars, features and advantages of the invention will become apparent in the following description taken about the drawings, in which: Figures 1a-c are sequential views of the stages of operation of an internal buffer in combination with an imagesetter and a film processor. Figure 2a is an illustration showing several latent images on a sample length of media. Figure 2b is an illustration showing several latent images cut from a continuous web. Figure 3a is a partial sectional view of a buffer roller drive mechanism in side elevation. Figure 3b is a partial sectional view of the buffer roller drive mechanism. Figure 4a is a partial sectional side view of a drive mechanism for the output door. Figure 4b is a partial sectional view of the drive mechanism for the output door. Figure 5 is a partial sectional view of the drive mechanisms for the rollers, input door and output door. Figure 6a is a view of a pair of drive rollers. Figure 6b is a cross-sectional view of the pair of drive rollers of Fig. 6a. Figure 7 is a diagrammatic view of an electronic prepress system including a control system and communication network. Referring to the Figure 1a, an internal buffer, generally referred to by reference numeral (40), is coupled with an imagesetter, generally referred to by reference numeral (20), and a film processor, generally referred to by reference numeral (60). In the imagesetter (20), a photosensitive material (50), hereinafter referred to as film, is fed from a continuous web supply roll (22) to a recording support surface (24) by a film transport system, generally referred to by reference numeral (26). The film (50) is transported by the film transporting system (26) from the imagesetter (20) into the buffer (40). The leading edge (52) (Fig. 2a) of the film is fed into the buffer (40) through film guides (42) (Fig. 3a) at the speed of the imagesetter (20). An input door (44) (shown in open position in Fig. 1a) is initially in an inclined position to serve as a guide for the film (50). The film (50) moves along the inclined door as the leading edge (52) approaches the nip (34) of the drive rollers (46). At the same time curved guide (48) urges the portion of film (50) immediately behind the leading edge (52) into a preformed downwardly curving shape, i.e. the same shape as the curved guide (48), to counteract the natural curvature of the film (50). An curved output door (49) (shown in closed position in Fig. 1a) is in a closed position initially, effectively forming a bridge for the film (50) to be guided over to the film processor (60). An input media sensor 32 senses the leading edge (52) of the film (50) entering the drive rollers (46). A sufficient amount of preliminary slack is fed into the buffer (40) by the imagesetter (20), while the leading edge is being pushed against the nip (34) of the drive rollers (46). Then the drive rollers (46) are actuated to grab the film (50). The film (50) passes through the drive rollers (46) and reaches an output media sensor (33), and the drive rollers (46) stop, thus holding the leading edge (52) of the film (50) in place as shown in Fig. 1a. The input door (44) opens and the preliminary slack grows into a larger slack loop as the leading edge (52) is held between the drive rollers (46) and the film (50) is fed by the imagesetter (20) from the web (22) into an input bin (37). The bin is essentially an open space for the film to form a slack loop and is not limited to the shown configuration. Referring to Figures 1b and 2b, following completion of the image or series of images, the film (50) is cut from the web (22) in the imagesetter (20) by a cutter (28) forming a trailing edge (54) and a sheet generally referred to by reference numeral (55), and a new leading edge on the web (42). The trailing edge (54) of the sheet (55) enters the buffer (40) and drops into the input bin (37). The drive rollers (46) are actuated to advance the leading edge (52) of the sheet (50) into the processor (60) at the operating speed of the processor (60). A processor input sensor 62 senses the film (50), and the output door drive motor (80) (Fig. 4a) opens output door (49). The drive rollers (46) transport the sheet (55) from the input bin (37) to an output bin (39) at a speed much faster than that of the processor (60) thereby forming a slack loop of film (50) as viewed in Fig. 1b. A new leading edge (52) can soon enter the buffer (40). Meanwhile the processor (60) removes the sheet (55) from the output bin (39). The input media sensor (32) detects the trailing edge (54) (Fig. 2a) of the sheet (50) as it leaves the input bin (37). When the trailing edge (54) passes the output media sensor (33), the input door (44) is then closed, and the drive rollers (46) are then stopped. A new leading edge (52) is fed into the buffer (40) while the trailing edge (54) of the first sheet (55) is still being removed from the output bin (39) of the buffer (40), as viewed in Fig. 1c. When the processor (60) has removed all the film (50) from the output bin (39), the processor input sensor (62) senses there is no film (50) present and the output door (49) is then closed. Referring to Figures 6a and 6b, a mechanical switch generally referred to by reference numeral (90), is used in cooperation with the optical input media sensor (32) (Fig. 1a) and is located near a reduced diameter portion (92) of the drive roller (46). The switch (90) is set so that lever arm (96) it pivots about point (94) into the reduced diameter portion (92) of the drive rollers (46) when the film (50) reaches it. This allows the film (50) to advance far into the nip (34) of the rollers (46) before the switch (90) is triggered. Referring to Figs. 3a, 3b, 4a, 4b, and 5 the drive systems for the drive rollers (46), and output door (49) are shown. Beginning with the roller drive mechanism shown in Figs. 3a and 3b, a roller drive stepper motor (70) is mounted to buffer housing (36) by conventional means (not shown) with its rotational axis parallel to the rotational axis of the drive rollers (46). The housing (36) rotatably supports two roller shafts (72, 74) that carry the drive rollers (46) nonrotatably. An extended portion of the roller shaft (72) has a gear (76) mounted on it that is driven by a pinion (78) on the motor shaft (79). When the roller drive motor (70) is on, the pinion (78) drives the gear (76) to rotate the roller shaft (72) that rotates its roller (46). The two rollers (46) are mounted such that they are in rolling contact with one another, thus when the shaft (72) is rotated, both rollers (46) are driven simultaneously. The drive mechanism for the output door (49) is shown in Figs. 4a, 4b and 5. The output door drive stepper motor (80) is mounted to the buffer housing (36) by conventional means (not shown) with its rotational axis parallel to the rotational axis of drive rollers (46). The output door drive motor (80) has a pinion (82) mounted to its shaft. A gear (84) is rotatably supported by the drive roller shaft (86), such that it can rotate freely upon it. A bracket (89) is fastened to the gear (84) by fasteners (88). The bracket (89) supports the output door (49), such that when the output door drive motor (80) is on, the pinion (82) drives the gear (84) and the attached bracket (89), causing the opening or closing of the output door (49) depending on the direction of rotation of the stepper motor (80). The operation of the input door drive mechanism is essentially the same as the output door drive mechanism. Shown in Fig. 7 are the electronic controls for the sensors and motors of the buffer (40) within the buffer controller generally referred to by reference numeral (140). Motor controls for the input door drive motor (85), output door drive motor (80), and roller drive motor (70), are indicated at (142), (144), (146), respectively. These control the start and stop, direction of rotation, rate of rotation, and number of steps rotated on each motor, and work in cooperation with microprocessor (150) which stores certain control sequences in memory. Media sensor driver/receiver (152) and door sensor driver/receiver (154), receive and process signals from the input and output media sensors (32), (33) and the input and output door sensors (31), (35) and also work with microprocessor (150). The communication network between the imagesetter (20), the buffer (40) and the processor (60) includes an imagesetter controller, generally referred to by reference numeral (120), the buffer controller (140), and a processor controller, generally referred to by reference numeral (160) which are connected in series by interface communication modules. The imagesetter controller (120) has two interface communication modules (122), (124) that communicate with the RIP (180) and with an interface communication module (156) in the buffer controller (140) respectively, to exchange information. Such control information is exchanged relating to length of film (50) in the buffer (40), length of the next image, resolution of the RIP image indicating film travel speed, and the operating state of the processor (60). The buffer controller (140) has a second module (158) that in turn communicates similar information with a module (162) in the processor controller (160). The buffer controller (140) working in cooperation with microprocessor (150), passes information between the imagesetter controller (120) and the processor controller (160). An important feature of the invention is the buffer (40) has only a single pair of rollers. The control and operation of the drive rollers (46) and a communication network between the buffer (40), imagesetter (20) and processor (60), enable the buffer (40) to successfully absorb the speed differential between the imagesetter (20) and processor (60) using a single pair of rollers. The operation of the buffer system with the communication network and electronic controls is as follows. The imagesetter controller (120) communicates with the buffer controller (140) through interface communication modules (122) and (156) respectively to determine the status of the buffer input bin (37). When the input bin (37) is ready, a signal is passed from the buffer controller (140) to the imagesetter controller (120) to actuate the film transport system (26) to deliver and feed the leading edge (52) of the film (50) into the buffer (40) at the speed of the imagesetter (20), which is a stored sequence initiated by the microprocessor (150). Input media sensor (32) senses the leading edge (52) of the film (50) entering the drive rollers (46). After the input media sensor (32) indicates the film (50) is entering the nip (34) a sequence of steps occur to form the preliminary slack loop. First the buffer controller (140) sends a message to the imagesetter controller (120) to start measuring how much film is moving into the buffer (40). Using the resolution of the image being imaged, and the number of scanlines being imaged, the imagesetter controller (120) calculates and measures the distance being traveled until a predetermined limit is reached. The predetermined limit will provide a sufficient amount of slack to prevent the image from being disrupted when the film (50) is grabbed by the motion of the drive rollers (46). The imagesetter controller (120) then signals the buffer controller (140) which activates the roller motor control (146) through microprocessor (150) to start the rollers (46) at the speed of the imagesetter. Then a portion of the preliminary slack is pulled in between the drive rollers (46) and the film (50) is advanced until it reaches the output media sensor (33), which, having sensed the leading edge (52), signals to stop the drive rollers (46). The imagesetter controller (140) passes information from the RIP (180) to the buffer controller (140) concerning the resolution of the each image, which dictates the speed at which an image will move through the imagesetter (20). The information is passed through microprocessor (150) to the roller motor control (146). The drive rollers (46) will start rolling at the same speed at which the imagesetter (20) is operating such that the film (50) is grabbed between the drive rollers (46), but not pulled on thereby disrupting the ongoing imaging at the image point (10) (Fig. 1a). Alternatively, to drive the drive rollers (46) at the speed of the imagesetter (20), the roller drive motor (70) is synchronized to match the speed of the imagesetter (20) by using an encoder 15 located in the imagesetter (20). The encoder (15) sends pulses through imagesetter controller (120) to the buffer controller (140) through interface communication modules (122), (156). The roller motor control (146) receives the pulses and thereby duplicates the speed at which the film (50) is moving in the imagesetter (20). When the film (50) passes through the drive rollers (46) and reaches the output media sensor (33) (Fig. 1a), the media sensor driver/receiver (152) processes a signal to the input door motor control (142) and to the roller motor control (146) through the microprocessor (150). Input door drive motor (85) is actuated, thereby opening the input door (44) to the input bin (37), and the roller drive motor (70) is switched off stopping the drive rollers (46). Communication occurs next between the communication interface modules (158), (162) of the buffer controller (140) and the processor controller (160). The buffer controller (140) checks whether the processor (20) is ready to process the sheet (55). The processor sensor (62) senses if there is film (50) present or not and conveys the message to the buffer controller (140). If the processor (60) is ready, the buffer controller (140) actuates the buffer drive rollers (46) through microprocessor (150) to feed the sheet (55) into the processor (60). If the processor (60) is not ready, the buffer controller (140) tells the imagesetter controller (120) to wait to cut. This exchange of information passes from the processor controller (160) to the buffer controller (140) to the imagesetter controller (120), due to the controllers being connected in series. The drive rollers (46) are actuated in response to a cut being made by the imagesetter (20) and hence the trailing edge (54) entering the buffer (40), and in response to the ready signal from the processor (60). A processor input sensor (62) senses the film (50) entering the processor (60). A signal is sent to the buffer controller (140) through interface communication modules (162), (158), indicating that it has the sheet (55). Therefore, microprocessor (150) initiates a sequence to output door motor control (144) such that output door drive motor (80) opens output door (49). Then the drive rollers (46) transport the sheet (55) from the input bin (37) to the output bin (39) at a speed much faster than that of the processor (60) thereby forming a slack loop of film (50) as viewed in Fig. 1b. Simultaneously, the processor (60) removes the sheet (55) from the output bin (39). The input media sensor (32) detects the trailing edge (54) of the sheet (55) as it leaves the input bin (37). Subsequently, the trailing edge (54) passes the output media sensor (33), the media sensor driver/receiver (152) activates the input door motor control (142) and the roller motor control (146) through the microprocessor (150), such that the input door drive motor (85) closes the input door (44), and the drive rollers (46) are stopped. The signal also relays a message from the buffer interface communication module (156) to the imagesetter interface communication module (122) that the buffer (40) is ready for a new sheet (55). When the processor (60) has removed all the film (50) from the output bin (39), the processor input sensor (62) senses there is no film (50) present. Consequently, the processor interface communication module (162) tells the buffer interface communication module (158) that it is ready for the next piece of film (50) and the microprocessor (150) initiates a sequence to output door motor control (144) to close output door (49). There are two modes of operation of the imagesetter (20). Referring to Figures 1a, b, c, 2, and 2a, b, in the first mode, several images are recorded onto one length of film (50) so as to use the buffer's full capacity. In this mode, the imagesetter controller (120) determines when to cut the film (50) from the web (22) and form a sheet (55) that does not exceed the buffer maximum. To do so, the imagesetter controller (120) checks at the start of each image whether the next image will fit into the buffer (40) or not. In the first mode of operation, the drive rollers (46) take up the leading edge (52) of the film (50) at the speed of the first image of a series of images to be formed on one sheet (55). Then the leading edge (52) is held in place as the incoming images form a slack loop in the input bin (37), until the series of images is complete and the sheet (55) is cut from the web (22). To determine if the next image to be recorded onto the film (50) will fit into the buffer (40), and where to cut, the microprocessor (150) computes the length of film (50) that has passed from the imaging point 10 into the buffer (40). Before the start of the next image at the imaging point (10), the RIP (180) and the imagesetter controller (120) exchange information through communication interface module (124). The length of the next image to be exposed is passed from the RIP (180) to the imagesetter controller (120) and it is added to the length of film (50) measured by the microprocessor (150) that is already in the buffer (40). The resulting total is compared to the buffer maximum value. If the total is below the buffer maximum, the imagesetter (20) starts the next image, adding onto the length of film (50) in the buffer (40). Also included in the computed total is the length of exposed film between the image point (10) and the cutter (16), which has not yet been measured by the microprocessor (150), but will be fed into the buffer (40) after the cut is made. If the total is above the maximum, the film (50) is advanced a predetermined amount so that the end of the image moves from the image point (10) to the cutter (16), and is cut. It is also an option of the imagesetter (20) to continue imaging as the film (50) is advanced to the cutter (16), so as not to waste unexposed film between images, for example, when additional RIP images are waiting to be recorded on the next sheet. This option will be described in the second mode of operation. The microprocessor (150) could also be used in coordination with encoder (15) to ensure accuracy in the calculations, i.e. ensure the film (50) moved the computed length. The encoder (15) could be located in either the imagesetter (20) or the buffer (40). Similarly, the microprocessor (150) could be in either the imagesetter controller (120) or the buffer controller (140). When a first image size is too small for the buffer (40), and the next image size when added to the first image size is too big for the buffer (40), the imagesetter controller (120) advances the end of the first image the appropriate amount to meet the required buffer minimum without adding on the next image. Referring to Fig. 2a, an example of several images exposed on a web of film (50) is illustrated. There are four exposed images (58) of varied lengths on one sheet (55). The leading edge (52) of the sheet (55) is equal to the length between the imaging point (15) and the cutter (16), shown in Fig. 1a, due to advancement of the previous image to beyond the cutter (16). The leading edge (52) always proceeds the trailing edge (54) through the buffer (40), and into the processor (60). The trailing edge (54) and the unexposed areas (56) between images, or the inter-image space, are arbitrary lengths selected by the operator which may be much smaller than the length of the leading edge (52). In the second mode of operation of the imagesetter (20), a cut is made after each image providing the image is of a minimum required length which is governed by the spacing of the rollers handling the film. Referring to Fig. 1a, it can be seen that the minimum lengths are the distance between the cutter (16) and the output media sensor (33), and between the drive rollers (46) and the processor rollers (64). The lengths of the images may vary from one to the next resulting in varied sheet lengths when the images are cut, as pictured in Fig. 2b. In the second mode, at the end of each image the film (50) is advanced a small selectable amount at the imaging point (15), forming a gap (59) or an inter-image space of unexposed film (50), as a designated cutting location. When the next image is started, the gap (59) will advance toward the cutter (16). To determine when the gap (59) will arrive at the cutting point, the RIP (180) tells the imagesetter controller (120) the size of the next image. The microprocessor (150) calculates the number of scan lines of the next image that will have to be imaged in order to move the center of the gap (59) to the cutter (16). As the next image is started, the calculated number of lines are imaged until the gap (59) arrives at the cutter (16). The imaging is suspended temporarily to cut at the approximate center of the gap (59), indicated by dotted line (57) in Fig. 2b. The imaging then resumes to complete the current image. This method can also be used in the first mode of operation when cutting between consecutive sheets of multiple images, to avoid a large leading edge on the next sheet. In the second mode, if an image size is below the buffer minimum, the imagesetter controller (120) will advance the end of the first image the appropriate amount to meet the required buffer minimum and then the sheet will be cut from the web. In a general application of the invention, material which is precut into uniform length sheets is used such that the precut sheets pass one at a time through the buffer. In this embodiment no cutting is necessary, but may be done if so desired. In an alternative embodiment, the imagesetter controller (120) has a third module (126) that communicates with module (164) in the processor controller (160) as indicated by a dotted connecting line (166) in Fig. 7. This communication network enables the three controllers (120), (140), (160), to exchange status information, report errors, indicate jamming, etc., directly to one another without having to pass through the buffer controller (140). In yet another embodiment, the imagesetter controller (120) and the buffer controller (140), or the processor controller (160) and the buffer controller (140), form a single electronic controller that has sub modules, resulting in a direct communication link between the imagesetter (20) and the processor (60). In a preferred embodiment, the buffer (40) is integral with an imagesetter (20), hence the name internal buffer. The buffer (40) is designed to fit in the space of and replace a take-up cassette of the imagesetter (20) such that the two can be used interchangeably if desired. Shown in Fig. 5 is the feature of the invention that integrates the buffer (40) into the imagesetter (20) to form one component. The buffer (40) is nested within a space 123 that is defined by an internal housing (125) of the imagesetter (20). This space (123) exists within the imagesetter (20) for the take-up cassette that is used to hold the entire wound length of exposed media in the prior art. The buffer mechanism (40) has the same dimensions as the old take-up cassette, thus making it possible to replace the take-up cassette and integrate the buffer (40) internally into the imagesetter (20). This reduces the number of components in the photographic imaging and developing system and saves floor space. Alternatively the buffer (40) can be integrated with the processor (60) in a similar manner. In both cases, although the buffer fits in the space of the take-up cassette, the open space below the housing in which the buffer is nested, is used to accommodate the slack loops of film.

Claims: An apparatus for buffering separate pieces of material, each with a leading edge (52) and a trailing edge (54), between two machines comprising: a first machine (20) having a first operating speed and a first controller (120); a second machine (60) having a second operating speed and a second controller (160) which is distinct from said first controller; a material buffer (40) disposed between said first machine (20) and said second machine (60), for taking up a first piece of material from said first machine (20) at said first operating speed and transferring said first piece of material to said second machine (60) at said second operating speed, said material buffer (40) being capable of taking up a second piece of material while said first piece of material is being transferred to said second machine (60) from said material buffer (40); characterized in that, said material buffer (40) being detachably coupled with said first machine (20) and said second machine (60) and further comprising a buffer controller (140) which is distinct from said first controller (120) and said second controller (160), and wherein said buffer controller (140) includes a communication interface (158, 162) for exchanging information between said material buffer (40) and said second machine (60) so that a communication network is provided. An apparatus for buffering separate sheets of material according to claim 1 wherein said material buffer (40) comprises a single pair of drive rollers (46) maintained in constant rolling contact with each other. An apparatus for buffering separate sheets of material according to claim 2, further comprising, a drive motor drive (70) in driving contact with one roller of said single pair of drive rollers (46), said drive motor (70) being driven by a motor controller (146) such that said single pair of drive rollers (46) operate at a first speed, while receiving said leading edge (52) of said first piece of material from said first machine (20), and at a second speed, while transferring said leading edge of said first piece of material to said second machine (60). An apparatus according to claims 2 and 3 wherein after said single pair of drive rollers (46) transfer said leading edge (52) of said first piece of material to said second machine (60) and after said trailing edge (54) is free from said first machine (20), said single pair of drive rollers (46) operate at a third speed to move said trailing edge (54) of said first piece of material beyond said single pair of drive rollers (46), said third speed being faster than said first speed and said second speed. An apparatus according to claims 2-4, further including, a second piece of material having a second leading edge and a second trailing edge and wherein said second leading edge is taken up by said single pair of drive rollers (46) after said first leading edge (52) exits from said single pair of drive rollers (46). An apparatus for buffering separate sheets of material according to any of the above claims, further comprising, a communication interface (122, 156) connected between said first machine (20) and said material buffer (40) such that information is exchanged between said first machine (20) and said material buffer (40) and between said first machine (20) and said second machine (60). An apparatus for buffering separate sheets of material according to any of the above claims, wherein said material buffer (40) removably replaces a take-up cassette in said first machine (20) and has approximately equal dimensions to said take-up cassette such that said material buffer (40) fits in a space (129) provided for said take-up cassette and may be easily interchangeable therewith. An apparatus for buffering separate sheets of material according to any of the above claims wherein said first machine (20) comprises a photographic recording device and said second machine (60) comprises a photochemical processor. A method for buffering separate pieces of material, each with a leading edge (52) and a trailing edge (54), between two machines comprising the steps of: advancing a first sheet of material from a first machine (20) at a first speed; receiving said first sheet of material from said first machine with a material buffer (40), disposed between said first machine (20) and a second machine (60), said material buffer (40) taking up said first piece of material from said first machine (20) at said first speed, said material buffer (40) being capable of taking up a second piece of material while said first piece of material is being transferred to said second machine (60) from said material buffer (40); characterized in communicating between said material buffer (40), which is detachably coupled with said first machine (20) and said second machine (60), and said second machine (60) information determining a status of said second machine, so that a communication network is provided. A method according to claim 9 further comprising the step of advancing said leading edge (52) of said first sheet of material from said material buffer (40) to said second machine (60) at a second speed corresponding to the speed of said second machine (60). A method according to claim 10 further comprising the steps of: receiving a signal in said material buffer (140) from said second machine (60), said signal indicating that said leading edge (52) of said first piece of material has been received by said second machine (60); receiving a signal in said material buffer (140) from said first machine (20), said signal indicating that said trailing edge (54) of said first piece of material is free from said first machine (20); advancing said trailing edge (54) through said material buffer at a speed which is faster than said first speed and said second speed while said leading edge (52) is advancing into said second machine (60) at said second speed. A method according to claim 11 further comprising the steps of: sending a signal from said material buffer (140) to said first machine (20), said signal indicating that said material buffer can receive a second sheet of material; advancing a second sheet of material from said first machine (20) to said material buffer (40) while said first sheet of material is advancing into said second machine (60). A method according to claim 9 further comprising the step of communicating information between said material buffer (40) and said first machine (20) to determine a status of said first machine. A method according to claim 9 further comprising the step of communicating between said second machine (60) and said first machine (20) and between said first machine (20) and said second machine (60) through said material buffer (40). A method according to claim 9 further comprising the steps of: determining a length of said first piece of material based on an recorded image size and a maximum length and a minimum length of material that said material buffer can accommodate; cutting said first piece of material from a web of material according to said determined length.

Inventors: GOODWIN ROBERT A, KRUPICA LIBOR, MORGAN PAUL W, GOODWIN, ROBERT A., KRUPICA, LIBOR, MORGAN, PAUL W.
Applicants: AGFA CORP, AGFA CORPORATION
Application year: 1994
Main classification: B65H20
IPC codes: G03D13, B65H35, B65H5, B65H20